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Molecular dynamics simulations of the growth of Ge on Si Y. Zhoua, A. Lloyd, R. Smith [et al.]

Contributor(s): Lloyd, Adam | Smith, Roger | Lozovoy, Kirill A | Voytsekhovskiy, Alexander V | Kokhanenko, Andrey P | Zhoua, YingMaterial type: ArticleArticleContent type: Текст Media type: электронный Subject(s): квантовые точки | молекулярная динамикаGenre/Form: статьи в журналах Online resources: Click here to access online In: Surface science Vol. 696. P. 121594 (1-9)Abstract: The initial stages of the growth of germanium on the dimer reconstructed Si(100) surface is modelled using molecular dynamics (MD). Pyramidal island structures are observed to form despite MD being carried out at a deposition rate faster than experiment. By an examination of transitions that can occur from intermediate structures that form in the MD simulations, growth mechanisms can be identified. The initial wetting occurs as a result of Ge atoms diffusing into the trenches between the dimer rows. This results in Ge–Ge or Ge–Si dimer chains growing in rows perpendicular to the original Si–Si dimer rows on the surface. It is shown how strained Ge pyramids with square bases can form by diffusing atoms joining together adjacent dimer rows. From these initial square-based structures, complex concerted motions are observed in which atoms in lower layers ‘climb up’ to higher layers. Similar structures grown in the pure Si case exhibit much higher energies barriers for the ‘climbing up’ process indicating that the effect of strain is to reduce the energy barriers for pyramid formation. In addition to the investigation of atomistic growth processes, surface energy effects are also examined, which show that a germanium-covered Si(100) surface containing shallow-angled pyramids is energetically more favourable than that grown as a flat monolayer.
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The initial stages of the growth of germanium on the dimer reconstructed Si(100) surface is modelled using
molecular dynamics (MD). Pyramidal island structures are observed to form despite MD being carried out at a
deposition rate faster than experiment. By an examination of transitions that can occur from intermediate
structures that form in the MD simulations, growth mechanisms can be identified. The initial wetting occurs as a
result of Ge atoms diffusing into the trenches between the dimer rows. This results in Ge–Ge or Ge–Si dimer
chains growing in rows perpendicular to the original Si–Si dimer rows on the surface. It is shown how strained
Ge pyramids with square bases can form by diffusing atoms joining together adjacent dimer rows. From these
initial square-based structures, complex concerted motions are observed in which atoms in lower layers ‘climb
up’ to higher layers. Similar structures grown in the pure Si case exhibit much higher energies barriers for the
‘climbing up’ process indicating that the effect of strain is to reduce the energy barriers for pyramid formation. In
addition to the investigation of atomistic growth processes, surface energy effects are also examined, which show
that a germanium-covered Si(100) surface containing shallow-angled pyramids is energetically more favourable
than that grown as a flat monolayer.

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